Abstract. Some of the author’s previous works, dealing with the classification problem for simply connected closed 6-manifolds, contain a construction of a certain “exotic” invariant Γ. This construction is substantially indirect and based on nontrivial calculations. In the present paper, a direct construction is suggested, which does not depend on the calculations mentioned and involves only some simple surgery, plus some well-known identities for Stiefel–Whitney and Pontryagin classes, namely, “modulo 2 ” and “modulo 4 ” Wu formulas
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